Process by which aluminum metal and its alloys may be applied to ferrous metal



Patented Dec. 15, 1925.

UNITED STATES PATENT OFFICE.

CARL W. PFEIL, OE GREENBANK, WASHINGTON.

PROCESS BY WHICH ALUMINUM METAL AND ITS ALLOYS MAY BE APPLIED TOFEIQBOUS METAL.

No Drawing.

To all whom it may concern:

Be it known that- I, CARL W. PFEIL, a citizen of the United States,residing at Grreenbank, in the county of Island and State of Washington,have invented Processes by Which Aluminum Metal and Its Alloys May beApplied to Ferrous Metals, of which the following is a specification.

My invention relates to the art of providing metals with a protectivecoating, as for instance, applying a coating of a rust and acidresisting metal to a baser metal.

The object of. my invention is to apply a metallic protective coating insuch a manner as to secure a joining of the protective and the basemetals in that close and intimate manner that the protective coatingcannot be sealed off, the union between the metals being'more in. thenature of an alloying of the two, rather than an adhesive contactbe-'tween them. I

The process employed by me in carrying out my invention 'will behereinafter described and the features thereof which are believed to benovel will be particularly defined by the claims.

. While the field for the use of my process is probably greater in theapplication of an aluminum coating to sheets of a ferrous metal for the'manufacture of a product usable as a substitute for tin plate, it isnevertheless adapted to the application of protective alloys having analuminum com-v ponent and also for application of such a protectivemetal coating to cast and wrought metals irrespective of their thicknessand bulk. I will herein more specifically describe the application of myinvention to providing an aluminum coating for sheet metal; it is,however, to be understood that this is not done as a'limitation to thisuse only, but only as illustrative of the principles to be employed andthe manner of securing the ,desired results.

It has been rather generally held that proper welding or soldering ofaluminum'to aluminum, or to other metals, is prevented by an oxide filmwhich promptly forms upon a newly formed surface of aluminum. Thistheory of an oxide film may or may not be correct. I have, however,found that if aluminum be reduced to very fine powderlike particles andduring such reduction'a- Application filed May 1,

- point 0 1922. Serial No. 557,705.

and the aluminum or aluminum alloy is ma-' terially facilitated orcontrolled by the electric relationship existing between the two and byelectric action occurring when theyare brought into contact.- Suchelectrical action is also heat.

I have noticed that success irr getting a welding or alloying unionbetween the base and coating metal appears to depend very much upon thebase metal being electronegative to the coating metal. It would-appearprobable that an action occurs which is of an electrolytical characterand this supplements the ordinary fusing action of heat.

The surface thus formed has the protective and resistant qualities ofthe material formingthe coating and cannot by ordinary means beseparated from the metal which forms the base.

As the protective material for the fine particles of the coating metal Ihave employed oils, fats, waxes, fatty acids, resins and the like, andother substances and combinations thereof capable of formingairexcluding films and of being volatilized or otherwise eliminated ordissipated by heat at tem eratures lower than the melting tithe coatingmetal used. The ideal is a substance or mlxture which will not bedissipated until the fusing temperature is nearly reached.

This protective material may be of animal, vegetable or' mineral origin.I have found a large number of products to be adapted for such use. Thechief requirement appears to be their ability to coat the metallicparticles with a thin film which excludes the air and the quality ofbeing volatilized or dissipated by heat at temperaprobably intensifiedby the tures below that of fusing of the coating metal. I

Among the substances which I have found adaptedrto this use are themineral oils, of which kerosene is a type; mineral waxes, of whichpara'fiin is, a type; vegetable. oils, of which palm oil is a type. Or Imay use combinations of two or more of suchsubstances as the protectivefilm forming material, this including chemicals such as ammoniumchloride.

In preparing the metal for the coating material I finely divide andgrind, or otherwise pulverize, it in a bath of the protective filmforming material. The means employed in grinding the metal is immaterialif it will reduce it to fine particles. It is desirable that theparticles be reduced as fine as possible. The result of this work is acolloidal-like sludge or paste which should contain the largest possibleamount of metallic particles. I

In carrying out the coating process this product is heated to atemperature which will vary with the metal contained therein and withthe kind of film forming material which has been used. The temperatureshould be as high as possible, less than that which will volatilize orotherwise eliminate the film forming material, or less than the fusingpoint of the metal, depending upon which is the lower.

The body of the metal to be coated is heated to a temperature in excessof that of the bath and is coated either by dipping the heated metal inthe bath or by applying-the bath to the heated metal, as best suits theconditions. If the body to be coated isdipped in the bath, it is lefttherein only momentarily. The heat of the metal base, being higher thanthat of the bath'dissipates a portion of the film forming agent. The

metal content of the bath adheres as a thin coating to the base.

The metal body ,being coated is further heated after removal from thebath, thus completing the driving oif'of the film forming materials fromthe compound which has adhered to the base. This coating has apparentlybeen alloyed with the base so as to secure the coating to be in effectan integral part of the base. There isno cleavage plane between the twowhich will permit separation.

The protective coating may be applied to the base or article to becoated, by brushing or flowing it thereon. The conditions as totemperatures should, however, be essentially the same. The heat andtemperature needed to evaporate or drive off the protective" film mustbe applied, in part at least, after the film has been a plied. Thefundamental temperature con itions which are desirable or necessary are,first, that the temperature of the metal bath be less than that whichwill volatilize or drive off the protective film forming material andthat of the metal base after the application of the film be such as willvolatilize or drive ofi this film forming material. 7

The temperature of the bath and of the metal base at the time of aplying the coating contributes to the perf ction of the union betweenthem, a higher temperature producing better results than a lowertemperature. I also prefer that the metal base be of a temperaturesomewhat above that at without immersion, or by partial immersion,

it is possible to apply a protective coat locally. The surface aftercoating may be rolled, burnished or given any treatment which may begiven to metals coated by other processes.

I have found a coating thus applied to be more perfect in its continuitythan an ordinary tinplate coating. It does not seem to ossess themicroscopical uncoated points or holes in the protective layer throughwhich acids may act upon the metal base and rust take place. I 1 'i Ihave found this process to be applicable to applying coatings ofaluminum or alloys in which aluminum forms a material part. The processis, however, not limited to use with these metals alone. One of thechief applications of this process is the applicaties against the actionof acids, corrosive agents and heat is superior to that of tin plate,both by reason of the superior resistant quality of aluminum to suchagents and by reason of its superior mechanical condition in its freedomfrom minute erforations and its higher resistance to eat and also itsnon-poisonous qualities.

Such coatings are superior to tin plate in this that heating to atemperature less than the melting point of aluminumm will not causeloosening of the coating from the base as may be done with tin plate.There ap pears to be an inter-penetration or alloying of the-coating andbase metal which prevents separation and is not affected by any heatwhlch will not actually melt the coating metal. c

The essential feature in the success of welding where at least one ofthe metals is aluminum or an aluminum alloy appearsto be the provisionof a fresh surface on the aluminum and protecting it from the action ofthe air by giving it a protective film, as of an oil or wax or otherair-excluding substances which has a hi h dissipating point, and theneliminating t is film at the time of joining the surfaces, whereby thealuminum or a uminum alloy is presented to the visible film formedthereon by the action of air whereby it readily forms atrue weldingunion.

While I have chiefly herein dwelt upon the application of a very thincoating of the protective metal and by the use of the protective metalin the form of powder, the

same principle is believed to apply to the union. of distinct sheets,the surfaces to be welded being first treated by grinding or otherwiseremoving a surface film and protecting this by a protective film untilthe welding action occurs.

Commercial aluminum powder -may be used by my process but the resultsare not as satisfactory. A coating made by using commercial aluminumpowder will scale, especially when plates so coated are bent or seamed.

' What I claim as my invention is i 1. The process ofproducing aprotective coating of one metal upon another which consists in veryfinely dividing the coating metal in a bath of a film producing material'which may be driven off by heat, applying the product thus formed tothe metal to be protected and heating to a temperature which will driveoff the protective film and fuse the coating and base metal.

2. The process of applying an aluminum coating to a base metal whichconsists in very finely dividing the aluminum in a bath of anair-excluding film-producing material,

applying the compound thus formed to the metal, to be coated andheating.

'3. The process of giving a metal a protective coating of anothermetal'which consists in grinding the coating metal while subjected to afilm producing agent, heating the-product thus produced to a temperaturebelow that which will dissipate the film, heating the metal to be coatedto a temperature higher than that required to dissipate the film andthen applying the coating product to the metal to be coated.

4. The process ofapplying an aluminum alloy coating to'another metalwhich consists in finely reducing the aluminum alloy metal whilesubjected to an air excluding film-producing agent, heating this productto a temperature below that-which -will dissipate the filmproducing'agent, heating the metal base which is to be coated to atemperature sufficiently higher to dissipate the film and applying thecoating product to the base. V

5. The process of applying an aluminum alloy coating to a ferrous metalwhich consists in finely dividing the coating metal under air-excludingconditions and while still subject to such air-excluding conditionsheating it and the metal to be cdated and bringing the two together.

6. The process of coating a ferrous metal with aluminum which consistsin grinding the aluminum under a bath of an air-extion temperature,applying a coating of the resulting mixture to the metal to be coatedand heating to -a temperature which will volatilize the air-excludingmedium used eluding medium having a high volatilizaing film and causingthe coating metal to adhere to the base by the action of heat.

8. The process of applying a protective aluminum coating to a base metalwhich consists in simultaneously finely dividing the aluminum andapplying thereto as divided an air-excluding film, applying said productto the metal tobe coated and then eliminating the coating film andcausing the aluminum to adhere to the base by the application ofheat'thereto;

9, The process of securing welding union with aluminum which consists inremoval of a surface film from the aluminum and at the same timeprovidin with an' air-protective film of a material which can bedisposed of by heat at a temperature not exceeding the melting point ofaluminum, applyin the aluminum to the surface to which it is to bejoined and heating to a temperature sufiicient to dissi ate saidprotective film and to produce wel ing umon.

10. The process of securing welding union with aluminum which consistsin giving the aluminum a fresh surface by abrasion andat the same timegiving it an airprotective film which may be dissipated the new surfaceby heat at a temperature slightly lower than the welding heat foraluminum, applying the aluminum to the surface to whichit is :GARL- w.PFEIL,

